Mechanical face seal assemblies provide a fluid seal between a housing member and a shaft, one of which is rotating with respect to the other. Typically, the housing is stationary while the shaft is rotating. The mechanical face seal assembly utilizes a seal washer and a seal seat having faces that engage with and seal against one another. Either the seal washer or seal seat is fixed to the stationary member while the other component is rotationally fixed to the rotating member so that the two rotate relative to one another. The seal between the contacting seal washer and seal seat prevents fluid loss between the shaft and the housing.
Mechanical seal assemblies typically have an elastomeric grommet having a rind portion stretched around the outer diameter of the mechanical seal seat for mounting and holding the seal seat into the bore of a pump component, such as a housing or impeller, and to provide frictional rotational drive therebetween. The grommet also provides a static seal between the seal seat and the pump component along with accommodating diametrical tolerances of the seal seat outer diameter and the pump component bore. In such designs, a rear wall portion of the grommet radiates radially inward from the rind portion to hold the grommet onto the seal seat when press-fitting the two components into the pump component bore and to provide a cushion between the back of the seal seat and the bottom of the pump component bore once the seal seat and grommet are pressed home.
A common alternative design is to provide an elastomeric grommet having a rind portion fitted into the inner diameter of a seal seat, for mounting and holding the seal seat onto a shaft (shaft sleeve or shaft extension) of a pump, to provide frictional rotational drive therebetween, to provide static sealing therebetween, and to accommodate diametrical tolerances of the seal seat inner diameter and the pump shaft outer diameter. In such designs, a rear wall portion of the grommet radiates radially outward from the rind portion and serves to hold the grommet onto the seal seat when press-fitting the two components onto the pump shaft and to provide a cushion between the back of the seal seat and a shoulder of a shaft, an impeller or other component fixed to the shaft that establishes the final axial location of the seal seat and grommet on the shaft.
In both of these designs, an increased radial squeeze of the grommet rind portion provides increased frictional rotational drive, static sealing, and tolerance accommodation between the seal seat and the pump component bore or shaft. The increased radial squeeze, however, can compromise ease of installation, distort the seal seat, and/or overstress, dislocate or damage the grommet. Conversely, a decreased radial squeeze of the grommet rind portion provides easy installation, but can compromise frictional rotational drive, static sealing, and tolerance accommodation between the seal seat and pump component bore or shaft. Thus, it would be advantageous to provide a seal seat assembly that provides the desired rotational drive, static sealing and tolerance accommodation while also providing an ease of installation. It would further be advantageous if such a seal seat assembly were axially compact such that the axial space required for the seal seat assembly is reduced and/or minimized.